Gd5Si2Ge2.2 alloy was synthesized by arc-melting and its phase components, microstructure, and especially the line features were investigated by X-ray diffraction （XRD）, scanning-electron microscope （SEM）, energy-dispersive spectroscopy （EDS）, and transmission-electron microscope （TEM）. Gd5Si2Ge2.2 consists of Gd5Si2Ge2-type and GdGe-type phases and presents eutectic characteristics. There are many regular line features on the Gd5Si2Ge2-type phase according to SEM. EDS shows that the line feature is not the Gd5（Si,Ge）3-type phase because Gd content decreases at the line features. Two types of line features are found in the fine microstructure of Gd5Si2Ge2-type phase by TEM. Selected area diffraction （SAD） confirms that both line features are not the secondary phase or twins. There is no changes observed in the microstructure of Gd5Si2Ge2.2 from room temperature to 1400 ℃ with in situ high temperature optical microscope, therefore, it is deduced that the line features observed by SEM are formed during the solidification.
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